Field of the Invention
The present invention relates to a hemagglutinin of influenza virus, and in particular relates to a hemagglutinin of influenza virus capable of inducing the production of specific neutralizing antibodies and providing cross-protection against viruses.
Description of the Related Art
Influenza is a recurrent worldwide disease that causes annual seasonal epidemics and pandemics. The virus has an extremely wide host range, from birds to various mammalian species including humans, poultry, swine, and horses (Kalthoff et al., 2010). Influenza viruses belong to RNA virus Orthomyxoviridae family and can be classified into type A, B, and C. The genome of influenza A virus contains eight negative stranded RNA segments that encode 11 viral proteins, including three surface proteins, hemagglutinin (HA), neuraminidase (NA), and matrix protein (M2). Other encoded proteins include RNA polymerase subunits (PB1, PB2, PA), nucleoprotein (NP), nonstructural proteins (NS1, NS2) and a newly discovered pro-apoptotic PB1-F2 protein (Viswanathan et al., 2010).
Highly pathogenic avian influenza (HPAI) virus cause hundreds of millions of birds have died and severe mortality within susceptible poultry species. A novel H1N1 swine origin influenza virus emerged to cause human influenza outbreaks in 2009. Since the hemagglutinin (HA) has a high variability during influenza virus evolution, development of multivalent vaccine of influenza virus is still a challenge.
Even if in one strain of single species virus, a high percentage of a variant is still found due to virus has very high genetic variability. The current influenza vaccine almost only provides protection against the homosubtypic influenza virus.
Based on HA structure, it can also be discussed in two components, globular head and stem region. However, the multivalent vaccine is still developed by modifying the globular head region of hemagglutinin, and this method has disadvantages including (1) High-conserved glycosylation sites are not observed in globular head region so that the vaccine does not have broad-spectrum protective effects; (2) Thus, the glycan on the globular head region is generally digested by restriction enzymes to improve the effect of multivalent vaccines. If the carbon chain of the glycan is shorter, the effect of multivalent vaccines is better. However, how many carbon chain of the glycosyl group can be digested is a challenge.